JP2001304968A - Method and device for measuring temperature of heated object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for precisely measuring the surface temperature of a heated body, especially all kinds of heated steel materials, with a radiation thermometer. SOLUTION: A reflection plate is provided close to the surface of a heated body whose temperature is to be measured, and a heat-shielding member is fitted to the rear surface of the reflection plate, so that the temperature of reflection plate approaches the surface temperature of the heated object. A through opening is provided between the reflection plate and the heat shielding member, and the surface temperature of the heated object is measured, while measurement wavelength is limited to 0.6 μm or less using the radiation thermometer provided behind the heat shielding member through the through opening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring method and apparatus suitable for measuring a surface temperature of a heated object, particularly a heated steel material such as a steel plate, a mold steel, and a steel slab.

[0002]

2. Description of the Related Art In a steel manufacturing process, it is extremely important to accurately measure the surface temperature of the steel in terms of process control and quality control. In general, a radiation thermometer is used for measuring the surface temperature of a steel material. In a heated steel material, since a temperature measurement region is 600 to 1400 ° C.,
A Si element using a solar cell is used as a detector for measuring temperature.

[0003] The Si element has a measurement wavelength sensitivity peak near 0.9 µm. In this wavelength band, the Si element is covered with a thick oxide film like a rolled steel material made of general carbon steel, and has a composition of an oxide film. However, it is considered that a material having a substantially constant temperature enables accurate temperature measurement because the emissivity of the oxide film is relatively high.

However, in a high Si content steel material, a stainless steel material, etc., since the thickness and composition of the oxide film change greatly, the emissivity of the surface oxide film changes, and as a result,
It has been experienced that when the surface temperature of these steel materials is measured with a radiation thermometer using a Si element as a detector, a large measurement error occurs.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems in measuring the surface temperature of heated high Si content steel, stainless steel, and the like. It is an object of the present invention to provide a method and an apparatus for measuring the temperature of a heated object which enable accurate temperature measurement of a heated steel material and which can be applied to surface temperature measurement of a heated object other than steel.

[0006]

According to a first aspect of the present invention, there is provided a method for measuring the temperature of a heated object, comprising the steps of: measuring a surface temperature of the heated object with a radiation thermometer; A reflector is arranged near the temperature measurement surface, and a heat insulating member is attached to the rear surface of the reflector so that the temperature of the reflector and the surface temperature of the heating object are close to each other. The surface temperature of the heating object is measured by limiting the measurement wavelength range to 0.6 μm or less by a radiation thermometer installed behind the heat insulating member through the through opening.

According to a second aspect of the present invention, there is provided a method for measuring a temperature of a heated object, wherein the difference between the temperature of the reflecting plate and the surface temperature of the heated object is maintained in a specific close range. Measuring the surface temperature of the heating object by

According to a third aspect of the present invention, there is provided an apparatus for measuring the surface temperature of a heating object using a radiation thermometer, comprising: a reflecting plate disposed close to a temperature measurement surface of the heating object; A heat insulating member attached to the rear surface of the reflector, a radiation thermometer installed behind the heat insulating member, a through-opening connected to the reflector and the heat-insulating member, and a measurement wavelength range through the through-opening; Is set to be 0.6 μm or less, and the temperature of the heated object is measured by a radiation thermometer.

According to a fourth aspect of the present invention, there is provided a temperature measuring device for a heated object according to the third aspect of the present invention, wherein a device for measuring the temperature of the reflector and a device for vertically moving the reflector and the heat insulating member are provided. If the difference between the temperature of the reflector and the surface temperature of the heated object exceeds a certain close range,
A control mechanism is provided for driving a device for raising and lowering the reflection plate and the heat insulating member so as to adjust the distance between the reflection plate and the surface of the heating object.

In the present invention, the radiation measuring wavelength of the radiation thermometer is 0.6 μm or less, preferably 0.5 to 0.6 μm.
And, close to the temperature measurement surface of the heating object, a reflector covered with a heat insulating material is arranged, and a pseudo black body condition is realized in the measurement part. Accurate temperature measurement is possible for steel materials.

The following characteristics can be obtained by setting the radiation measuring wavelength of the radiation thermometer to 0.6 μm or less. (1) In the case of a normal heated steel material, the emissivity of the oxide film shows a high value of 0.8 or more for almost all materials. (2) The n value of the radiation thermometer (n = 14388 / λT, λ is the measurement wavelength (μm) of the radiation thermometer, and T is the measurement temperature (K)) is increased, and the measurement error with respect to the fluctuation of the emissivity is increased. Become smaller.

By arranging a reflector covered with a heat insulating material close to the temperature measuring surface of the heating object, the following characteristics can be obtained. (1) If the measurement wavelength of the radiation thermometer is shortened, the influence of the ambient light is increased. However, the influence of the ambient light can be reduced by the light blocking effect of the reflector. (2) When the reflector is heated, the radiant energy from the reflector and the radiant energy from the surface of the heating object cause multiple reflections between the reflector and the heating object, and a pseudo black body occurs at the temperature measurement portion. By realizing the condition, the influence of the emissivity can be further reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the effect of a temperature measurement wavelength of a radiation thermometer on a measurement error will be considered. Stainless steel plate without oxide film (original plate) and stainless steel plate with oxide film of various thickness formed on the surface (both SUS304
FIG. 4 shows the relationship between the emissivity of the steel sheet) and the measurement wavelength in comparison with the relationship between the emissivity of the hot-rolled steel sheet and the measurement wavelength. The emissivity was measured using a high-sensitivity spectrophotometer after charging the material into a vacuum furnace and heating the stainless steel plate to 850 ° C and the hot-rolled steel plate to 530 to 770 ° C.

As shown in FIG. 4, the emissivity of a stainless steel plate having a glossy surface without an oxide film is low, but when an oxide film is formed, the emissivity sharply increases in a short wavelength region.
In particular, it is recognized that there is a large difference in the emissivity between the wavelength around 0.5 to 0.6 μm and the vicinity of 0.9 μm used in a normal radiation thermometer. Since the high emissivity of the object to be measured is important for performing accurate temperature measurement, the measurement wavelength is set to a range of 0.6 μm or less, for example, 0.
It can be seen that setting the thickness to 5 to 0.6 μm is advantageous in measuring the temperature of a steel material having an oxide film on the surface.

The relationship between the measurement wavelength and the temperature error is expressed by the following equation. δT / T = (1 / n) (δε / ε)-(1) Equation n = 14388 / λT- (2) Equation δT is a temperature error caused by a change in emissivity, T
Is the measured temperature (K), δε is the variation of the emissivity causing a temperature error, ε is the emissivity of the steel material, and λ is the measurement wavelength (μm) of the radiation thermometer.

As can be seen from the above equations (1) and (2),
If the measurement wavelength is halved, the n value is doubled, and the temperature error due to emissivity variation is halved. As described above, if the measurement wavelength is shortened, accurate temperature measurement can be performed.

As a specific example, Table 1 shows temperature errors when the surface temperature of a stainless steel plate was measured at measurement wavelengths of 0.5 μm and 0.95 μm. In Table 1, the temperature indication is the temperature indication when the emissivity of the thermometer is set to 1.0, and the error is the difference temperature from the value measured by the thermocouple. As shown in Table 1, when the measurement wavelength is 0.5 μm, 0.95 μm
The error is reduced to about 1/4 as compared with the case of. That is, this example shows that the effect of emissivity can be significantly reduced by selecting the measurement wavelength.

[0018]

[Table 1]

Next, the effect on temperature measurement when a reflector having a heat insulating structure (for example, one in which a heat insulating member is attached to the rear surface of white alumina) is arranged near a heating object, for example, a surface temperature measuring portion of a steel plate. Considering this, the following equation holds for the transfer of radiant energy generated between the steel plate and the reflector. _{G 1 = e a F (t} a) + G 2 (1-e a) - (3) G 2 = e c F (t c) + G 1 (1-e c) - (4) G 1 is steel Radiant energy intensity from
₂ is the radiant energy intensity from the reflector to the steel plate, e _a
Is the emissivity of the steel plate, t _a is the temperature of the steel plate, F (t) is the energy intensity emitted by the black body at the temperature T, e _c is the emissivity of the reflector, and t _c is the temperature of the reflector.

When G ₂ is eliminated from the above equations (3) and (4), the following equation is obtained. _{G 1 = {e a F (} t a) + e c (1-e a) F (t c)} / {1- (1-e c) (1-e a)} - (5) G 1 is , A radiation temperature signal measured by the radiation thermometer.

When the rear surface of the reflector is insulated, the surface temperature t _c of the reflector disposed close to the surface of the steel plate is heated to a temperature close to the steel material temperature. As an example, Table 2 shows the relationship between the steel plate temperature t _a and the reflection plate temperature t _c . This relationship is measured by placing a disk-shaped reflector (diameter: 0.3, emissivity: 0.3, the back surface of which is covered with a heat insulating material having a thickness of about 10 cm) 30 cm above the steel plate. It was done.

[0022]

[Table 2]

Using the values in Table 2, for example, when the steel plate temperature is 9
Table 3 shows the results obtained by calculating the steel sheet temperature at 00 ° C. and the indication of the radiation thermometer by the above equation (5). However, the measurement wavelength is 0.5 μm. As shown in Table 3, by arranging the reflection plate, it is recognized that the results of Table 1 are improved and more accurate temperature measurement is performed.

[0024]

[Table 3]

The more accurate temperature measurement is performed by disposing the reflector, as can be seen from the above equation (5), when the reflector is heated, the radiation energy from the surface of the reflector and the steel plate This is because the radiant energy from the surface causes multiple reflections, and a pseudo blackbody condition is realized near the temperature measurement unit.

When the pseudo blackbody condition is realized, the radiation energy intensity G ₁ from the steel plate surface measured by the radiation thermometer is measured.
And the temperature of the reflector are equal, and t
Since the _{a = t c = t, (} 5) G 1 of the _{formula, G 1 = {e a F} (t) + e c (1-e a) F (t)} / {1- (1-e _{c) (1 -e a)}} = F (t) - (6), G 1 = G 2 - (7) becomes, G _1, taken independent of the emissivity of the steel sheet, the temperature t This is equivalent to measuring a black body, and accurate temperature measurement is performed regardless of the emissivity of the steel sheet.

[0027] The inventors first placed a shielding member facing the surface of the heated steel material, attached a heat insulating member to the rear surface of the shielding member, and passed through a through-opening connected to the shielding member and the heat insulating member. A device that measures the surface temperature of the heated steel by detecting the radiant energy from the heated steel with a radiation thermometer installed behind the heat insulating member, measures the temperature of the shielding member, and measures the temperature of the surface of the heated steel If the difference is within a specific close range, the pseudo black body condition is realized, and the temperature indicated by the radiation thermometer indicates the temperature of the steel surface almost accurately. Indicates the actual surface temperature of the steel material to be heated, and if the temperature indicated by the radiation thermometer deviates significantly from the surface temperature of the heated steel material, the temperature indicated by the radiation thermometer will Surface temperature Temperature measurement method of heating an object which is to make modifications to approaches proposed. (Japanese Patent Application No. 10-
No. 218950)

Also in the present invention, the temperature of the reflection plate is measured with a thermocouple or the like, and the difference from the temperature indicated by the radiation thermometer is monitored, whereby the above-mentioned Japanese Patent Application Laid-Open No. H10-157,1991 has been proposed.
In the same manner as the principle described in Japanese Patent Application No. 0-218950, it is possible to confirm whether or not good measurement accuracy has been realized. If the indication by the radiation thermometer greatly deviates from the surface temperature of the heated steel sheet, By using the same means as in Japanese Patent Application No. 10-218950, it is possible to modify the indication by the radiation thermometer so as to approach the surface temperature of the heated steel material.

[0029]

Embodiments of the present invention will be described below. Referring to one embodiment of the temperature measuring device according to the present invention, as shown in FIG. 1, a reflecting plate 2 disposed close to a temperature measuring surface of a heating object S, and attached to a rear surface of the reflecting plate 2. A heat-insulating member 3 and a radiation thermometer 4 installed behind the heat-insulating member 3 are provided. The temperature measuring device 1 is configured to perform measurement with the measurement wavelength range of the radiation thermometer limited to 0.6 μm or less, preferably 0.5 to 0.6 μm.

For example, the reflecting plate 2 is made of a white alumina having a diameter of 30 cm, its back surface is covered with a heat insulating member 3 having a thickness of 10 cm, and a reflecting plate 6 made of a stainless steel plate.
Is attached. The reflection plate 6 is attached as needed, and depending on the embodiment, the attachment can be omitted. Numeral 8 denotes a heat-resistant tubular member such as a steel pipe, which preferably has a structure in which the inside is water-cooled.

As shown in FIG. 3, the temperature measuring device shown in FIG. 1 is installed in an annealing line of a stainless steel plate comprising a heating zone 15 and a soaking zone 16 so that the stainless steel plate (hereinafter referred to as heating The temperature of the steel sheet S) was measured with a radiation thermometer. Further, a thermocouple 9 for actually measuring the temperature of the reflection plate 2 is attached to the temperature measuring device 1 (FIG. 1).
The reference thermometer 7 (FIG. 1) equipped with the i thermometer was brought close to the heated steel sheet S, and the surface temperature of the heated steel sheet S was also measured.
Table 4 shows the measurement results.

[0032]

[Table 4]

As shown in Table 4, the results of temperature measurement according to the present invention showed good measurement accuracy. The difference between the indication of the radiation thermometer and the temperature of the reflector 2 is within 30 ° C. Further, the reason why the instruction of the radiation thermometer is higher than the temperature actually measured by the reference thermometer is because the accuracy of the reference thermometer is slightly lower.

In the actual temperature measurement, as shown in FIG. 1, a device 12 for measuring a distance H (FIG. 1) between the heated steel sheet S and the reflector 2 is installed, and the reflector 2 measured by the thermocouple 9 is installed. The difference between the temperature of the heating steel sheet S and the surface temperature of the heating steel sheet S detected by the radiation thermometer 4 is calculated by the signal processing device 10, and when the difference exceeds a specific close range, the surface of the heating steel sheet S The reflector 2 and the heat insulating member 3 are moved up and down via the control device 11 in order to adjust the distance H between the reflector 2 and the temperature of the reflector 2 and the surface temperature of the heated steel plate S to be within a certain range. Preferably, the device 13 is driven and the interval H is adjusted (smaller) to maintain accurate temperature measurements.

In order to bring the reflecting plate 2 as close as possible to the surface temperature of the object to be heated and to improve the temperature measurement accuracy, a heater is embedded in the heat insulating member 3 to heat the reflecting plate 2 to prevent heat loss. In this case, a heat flow meter may be attached in place of the thermocouple, and the heater may be heated so that the heat flow in the heat insulating member becomes zero to prevent heat loss.

In an actual production line, for example, a hot rolling line, it is not desirable to always arrange a reflector near an upper portion of a steel plate because the rolling operation is hindered. In this case, as shown in FIG. 2, guide rolls 14 capable of contacting the heating steel plate S are provided on both sides of the reflection plate 2 so that the reflection plate can be brought close to the steel plate only during the temperature measurement. , Lower the device at the time of measurement,
Is preferably brought close to the surface of the heated steel sheet S and the temperature is measured.

[0037]

According to the present invention, there is provided a method and an apparatus for accurately measuring the surface temperature of a heated object, in particular, all kinds of heated steel materials by using a radiation thermometer. Also, during measurement, ensure that the indication from the radiation thermometer accurately indicates the surface temperature of the heating object.If the indication from the radiation thermometer deviates significantly from the surface temperature of the heating object, the radiation temperature A method and apparatus for measuring the temperature of a heated object is provided wherein the meter indication can be modified to approach the surface temperature of the heated object. The device according to the invention also allows an accurate measurement of the surface temperature of a moving heated object.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a measurement system of the present invention.

FIG. 2 is a view schematically showing an embodiment of the apparatus of the present invention.

FIG. 3 is a diagram showing an example of a mode of use of the device of the present invention.

FIG. 4 is a graph showing the relationship between the emissivity of an object to be measured and the measurement wavelength in temperature measurement by a radiation thermometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Temperature measuring device 2 Reflector 3 Insulation member 4 Radiation thermometer 5 Through-opening 6 Reflector 7 Reference thermometer 8 Heat-resistant tubular member 9 Thermocouple 10 Signal processing device 11 Controller 12 Distance H measuring device 13 Vertical moving device 14 For guide Roll 15 Heating zone 16 Soaking zone S Heated object (heated steel plate)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiro Sugiyama 1-3-2 Kitaaoyama, Minato-ku, Tokyo Inside Tokai Carbon Co., Ltd. (72) Inventor Park Wen-zhen Inventor No. 1 Goesdong-dong, Nam-gu, Pohang, Gyeongsangbuk-do Republic of Korea F-term in Pohang Integrated Steel Corporation 2G066 AA13 AC11 BA08 BB01

Claims (4)

[Claims] 1. A method for measuring a surface temperature of a heating object using a radiation thermometer, comprising: disposing a reflector close to a temperature measurement surface of the heating object; attaching a heat insulating member to a rear surface of the reflector; Temperature and the surface temperature of the heating object are made close to each other, and the measurement wavelength range is set to 0.6 μm or less by a radiation thermometer installed behind the heat insulating member through the through-opening connected to the reflector and the heat insulating member. A method for measuring the temperature of a heating object, characterized in that the surface temperature of the heating object is measured only in a limited manner. 2. A temperature measurement of a heating object, wherein a surface temperature of the heating object is measured by a radiation thermometer while a difference between a temperature of the reflection plate and a surface temperature of the heating object is maintained in a specific close range. Method. 3. An apparatus for measuring a surface temperature of a heating object with a radiation thermometer, comprising: a reflector disposed in close proximity to a temperature measuring surface of the heating object; a heat insulating member attached to a rear surface of the reflector; A radiation thermometer provided behind the heat insulating member, a through-opening is connected to the reflector and the heat-insulating member, and the measurement wavelength range is limited to 0.6 μm or less through the through-opening. An apparatus for measuring the temperature of an object in a heating furnace, the apparatus being configured to measure the temperature of the object to be heated. 4. A device for measuring the temperature of the reflector and a device for moving the reflector and the heat insulating member up and down are provided, and the difference between the temperature of the reflector and the surface temperature of the heating object is close to a specific value. A control mechanism for driving a device that raises and lowers the reflection plate and the heat insulating member so as to adjust the distance between the reflection plate and the surface of the heating object when exceeding the range. 3. The temperature measuring device for a heated object according to 3.